With an increase in the memory capacity of a semiconductor memory device, the size of the memory cells forming the semiconductor memory device has a tendency to decrease. When the size of the memory cells is decreased, characteristics of the transistors which form the memory cells are affected by a dispersion of the transistors caused by the manufacturing process. For example, as the width of a window for an electrode, such as an emitter electrode varies, or the size of the window for an electrode varies, due to the manufacturing process, the forward current of the diode between the base and emitter of the transistor varies. If the position of the window for the electrode is not at the correct position, the base resistance of the transistor varies. When the characteristics of the transistors which form the memory cells vary due to the manufacturing process, as mentioned above, sometimes, information stored in the memory cells cannot be read out or, the information may be destroyed.